The invention relates to an air vortex mill for mill-drying a flowable product with a gas-air flow-through mill chamber with several grinding stages arranged in the mill chamber, formed by a rotor comprising a multitude of grinding plates and a stator housing, as well as a device for transporting the product into the mill chamber.
Utilization of an air vortex mill for not only grinding but also and predominantly for drying of wet products is known from U.S. Pat. No. 5,984,212. It is, however, a problem if the products to be dried involve viscous, sticky, oily products, which, if one doses the product laterally into the mill chamber, deposit themselves upon the rotating grinding plates, produce baked-on deposits at the outer walls—in the worst case block the mill and cause it to shut down—and which do not become dry in the short dwelling time.
In the past, one availed oneself of the remedy by first mixing these products outside of the rotor and/or prior to introduction into the rotor, in a continuously or intermittently operating mixing system with already dried product or with other products, so that said entire mixture resulted in a crumbly mass, which could be transported via proportioning screw, and which was then conducted to the rotor for mill-drying.
Such work involving the mixing drum constitutes additional equipment expense, added thermal burden for the retro-mixed product, an additional burden perhaps also for the mill-drying process, need for additional space including further drawbacks.
An attempt to laterally pipe in similar products failed a number of times—the machine either clogged up with too large a nozzle cross-section aperture, or with sufficiently small nozzle cross-section and proper supply pressure, the nozzle became clogged, in particular due to the high temperature of the hot air which flows past the nozzle and the relatively small nozzle cross-section.
In some products, impurities cannot be avoided or cannot be removed through filtration, in particular when viscous products are involved, so that the nozzles can also be come clogged by foreign bodies in the suspension. Utilization or pre-mixing of compressed air with the nozzle and possible cooling of the nozzles did not produce the desired result.
From DE 38 11 910 A1 it is known to press wet product in foil-like thin fashion through a slit extending approximately parallel to the rotor axis, directly into the area between stator housing and grinding plates. This solution did not find acceptance on the market.
The object of the present invention is based on eliminating the problems of the initially described kind in an air vortex mill.